Discrimination device, discrimination method, and discrimination program

Abstract

To suppress wrong discrimination of the type of a recording medium in a wide range.SOLUTION: An image-forming device 1 includes: an acquisition section for acquiring respective measurement values of multiple discrimination indexes used for discriminating the type of a recording medium for the recording medium; a discrimination section for discriminating the type of a recording medium from among multiple recording medium types on the basis of a comparison result between a measurement value and a threshold in each of multiple discrimination indexes; an input section for receiving operation for inputting the type of a recording medium; and a changing section for specifying a discrimination index of an object for changing a threshold from among multiple discrimination indexes and for changing the threshold of a discrimination index of the object such that the type of a recording medium is discriminated as an inputted type when the discriminated type differs from the inputted type.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a discrimination device, a discrimination method, and a discrimination program for discriminating the type of a recording medium on which an image is formed from a plurality of recording medium types.

Background Art

[0002] In order to improve the quality of an image formed by an image forming apparatus, it is necessary to change the process conditions (e.g., fixing temperature) of the image forming apparatus according to the characteristics of the recording medium (e.g., paper) on which the image is formed. Conventionally, there has been known an image forming apparatus that optically detects the characteristics of a recording medium and discriminates the type of the recording medium based on the detection result. In these image forming apparatuses, the type of the recording medium may be misdiscriminated due to variations in the recording medium itself, variations in the components of the apparatus, and / or variations in the assembly of the components.

[0003] The image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-96617 determines that the type of the recording material is the paper type specified by the user when the measured value obtained by detecting the reflected light or transmitted light from the recording material is within the user-specified region.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2008-96617, the type of the recording medium is correctly discriminated within the user-specified region, but the type of the recording medium may be misdiscriminated in a region outside the user-specified region. There is a need to suppress misdiscrimination of the type of the recording medium over a wider range.

[0006] One of the purposes of this disclosure is to more broadly suppress the misidentification of the type of recording medium. [Means for solving the problem]

[0007] A discrimination device according to a certain aspect of this disclosure includes: an acquisition unit that acquires measured values ​​for each of a plurality of discrimination indicators used to discriminate the type of recording medium with respect to a recording medium; a discrimination unit that discriminates the type of recording medium from among a plurality of recording medium types based on the result of comparing the measured value and a threshold value for each of the plurality of discrimination indicators; an input unit that accepts an operation to input the type of recording medium; and a modification unit that, when the discriminated type and the input type are different, identifies a discrimination indicator whose threshold value should be changed among the plurality of discrimination indicators, and modifies the threshold value of the target discrimination indicator, so that the type of recording medium is discriminated against as the input type.

[0008] Preferably, the multiple recording media types include at least two of plain paper, recycled paper, coated paper, and colored paper.

[0009] Preferably, each of the multiple discriminant indicators is the relative value of the transmittance of two types of light with different wavelengths, or the relative value of the reflectance of the two types of light. The threshold value for each of the multiple discriminant indicators is set according to the IR transmittance, which is the infrared transmittance of the recording medium.

[0010] Preferably, the modification unit changes the threshold values ​​for each IR transmittance of the target discrimination index by the same amount all at once.

[0011] Preferably, the modification unit determines the amount of change to the threshold based on the difference between the measured value and a threshold corresponding to the IR transmittance of the recording medium.

[0012] Preferably, the modification unit determines the amount of change to the threshold based on the measured values ​​of the target discrimination index for multiple recording media.

[0013] Preferably, the input unit accepts an operation to input the number of recording media to be used to determine the amount of change.

[0014] Preferably, if multiple recording media types include colored paper, the multiple discrimination indicators include multiple colored paper discrimination indicators. The discrimination unit determines that a recording media is colored paper if the measured value of at least one of the multiple colored paper discrimination indicators indicates colored paper. The discrimination unit determines that a recording media is not colored paper if the measured value of any of the multiple colored paper discrimination indicators does not indicate colored paper. If the recording media is determined to be not colored paper and the input type is colored paper, the modification unit identifies multiple colored paper discrimination indicators as the target discrimination indicators, calculates the amount of threshold change based on the difference between the measured value and the threshold of the colored paper discrimination indicator with the smallest difference among the multiple colored paper discrimination indicators, and modifies the threshold of each of the multiple colored paper discrimination indicators by the amount of change.

[0015] Preferably, if multiple thresholds are set for the discrimination index of the target, the modification unit modifies all of the thresholds by the same amount at once.

[0016] Preferably, the relationship between the threshold and the IR transmittance is expressed by a linear function.

[0017] Preferably, the modification unit converts the difference into a number of steps based on a predetermined step unit, and determines the number of steps as the amount of modification.

[0018] Preferably, the discrimination device further includes a display unit that displays the amount of change.

[0019] Preferably, the discrimination device further includes a display unit that displays a screen for selecting the type of recording medium from a plurality of recording medium types. The discrimination device accepts the type of recording medium according to the user's operation on the screen.

[0020] According to another aspect of the present disclosure, a discrimination method includes: obtaining measurement values of each of a plurality of discrimination indicators used for discriminating the type of a recording medium for the recording medium; discriminating the type of the recording medium from among a plurality of recording medium types based on comparison results between the measurement values and threshold values for each of the plurality of discrimination indicators; receiving an operation of inputting the type of the recording medium; when the discriminated type and the input type are different, identifying a discrimination indicator that is a target for changing the threshold value among the plurality of discrimination indicators, and changing the threshold value of the target discrimination indicator so that the type of the recording medium is discriminated as the input type.

[0021] A discrimination program according to another aspect of the present disclosure causes a computer to execute the above-described discrimination method.

Advantages of the Invention

[0022] According to the present disclosure, it is possible to suppress, in a wider range, the incorrect discrimination of the type of a recording medium.

Brief Description of the Drawings

[0023] [Figure 1] It is a diagram showing an example of an image forming apparatus in the present embodiment. [Figure 2] It is a diagram showing an example of the hardware configuration of an image forming apparatus in the present embodiment. [Figure 3] It is a diagram showing an example of a media sensor in the present embodiment. [Figure 4] It is a diagram showing an outline of processing of an image forming apparatus in the present embodiment. [Figure 5] It is a diagram showing an example of a graph of a color paper discrimination index A1 in the present embodiment. [Figure 6] It is a diagram showing an example of a graph of a color paper discrimination index A2 in the present embodiment. [Figure 7] It is a diagram showing an example of a graph of a coated paper discrimination index in the present embodiment. [Figure 8] It is a diagram showing an example of a graph of an old paper pulp discrimination index in the present embodiment. [Figure 9]This figure shows the types of paper that can be identified by the combination of the colored paper identification index, the coated paper identification index, and the recycled paper pulp identification index in this embodiment. [Figure 10] This figure shows candidate discriminant indicators for which the threshold value is to be changed in this embodiment. [Figure 11] This is a flowchart showing part of the adjustment process procedure in this embodiment. [Figure 12] This flowchart shows the remaining steps of the adjustment process in this embodiment. [Figure 13] This figure shows an example of a screen that accepts an operation to instruct the start of the adjustment process in this embodiment. [Figure 14] This figure shows an example of a screen that accepts an operation to input the type of recording medium in this embodiment. [Figure 15] This figure shows an example of a screen that displays the adjustment details in this embodiment. [Figure 16] This figure shows an example of a screen indicating that no adjustment was made in this embodiment. [Figure 17] This figure shows the measured values ​​of each discrimination index for the paper being discriminated against in Examples 1 to 4, the threshold corresponding to the IR transmittance of the paper being discriminated against, and the difference between the measured value and the threshold. [Figure 18] This graph shows the relationship between the measured value of the color paper discrimination index A1 for the paper being discriminated against in Examples 1 to 4 and the threshold value corresponding to the IR transmittance of the paper being discriminated against. [Figure 19] This graph shows the relationship between the measured value of the color paper discrimination index A2 for the paper being discriminated against in Examples 1 to 4 and the threshold value corresponding to the IR transmittance of the paper being discriminated against. [Figure 20] This graph shows the relationship between the measured value of the coated paper discrimination index for the paper being discriminated against in Examples 1 to 4 and the threshold value corresponding to the IR transmittance of the paper being discriminated against. [Figure 21]This graph shows the relationship between the measured value of the recycled pulp discrimination index for the paper being discriminated against in Examples 1 to 4 and the threshold value corresponding to the IR transmittance of the paper being discriminated against. [Figure 22] This figure shows the slope and intercept of the reference line for each discriminant index in Examples 1 to 4. [Figure 23] This figure shows the step units used when determining the amount of threshold change in Examples 1 to 4. [Figure 24] This figure shows the amount of threshold change in Examples 1 to 4. [Figure 25] This figure shows the positions of the reference lines LB1 and LB2 on the coated paper discrimination index graph before and after the adjustment process for Example 1. [Figure 26] This figure shows the positions of the reference lines LB1 and LB2 on the coated paper discrimination index graph before and after the adjustment process for Example 2. [Figure 27] This figure shows the position of the reference line LC on the graph of the recycled paper pulp discrimination index before and after the adjustment process for Example 2. [Figure 28] This figure shows the position of the reference line LA2 on the graph of the color paper discrimination index A2 before and after the adjustment process for Example 3. [Figure 29] This figure shows the positions of the reference lines LB1 and LB2 on the coated paper discrimination index graph before and after the adjustment process for Example 3. [Figure 30] This figure shows the positions of the reference lines LA11 and LA12 on the graph of the color paper discrimination index A1 before and after the adjustment process for Example 4. [Figure 31] This figure shows the position of the reference line LA2 on the graph of the color paper discrimination index A2 before and after the adjustment process for Example 4. [Figure 32] This figure shows an example of a screen that accepts input for the type of recording medium in Modification Example 2. [Modes for carrying out the invention]

[0024] Hereinafter, embodiments and modified examples according to the present disclosure will be described while referring to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Note that the embodiments and modified examples described below may be selectively combined as appropriate.

[0025] [Embodiment] <A. Configuration of Image Forming Apparatus> Referring to FIGS. 1 to 3, the configuration of the image forming apparatus in the present embodiment will be described. FIG. 1 is a diagram showing an example of the image forming apparatus in the present embodiment. FIG. 2 is a diagram showing an example of the hardware configuration of the image forming apparatus in the present embodiment.

[0026] Referring to FIGS. 1 and 2, the image forming apparatus 1 forms an image on a sheet. Further, the image forming apparatus 1 discriminates the paper type from a plurality of paper types based on the comparison result between the measured value and the threshold value in each of a plurality of discrimination indexes. The image forming apparatus 1 is an example of the "discrimination device" in the present disclosure. The sheet is an example of the "recording medium" in the present disclosure.

[0027] The image forming apparatus 1 includes a control device 10, a paper feeding unit 15, a media sensor 20, an image forming unit 30, a fixing unit 40, an operation panel 50, and a communication interface 60. The control device 10, the paper feeding unit 15, the media sensor 20, the image forming unit 30, the fixing unit 40, the operation panel 50, and the communication interface 60 are connected by a bus 99.

[0028] The control device 10 includes a processor 11, memory 12, and storage 13. The processor 11 is composed of, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The memory 12 is composed of, for example, a volatile storage device such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory). The storage 13 is composed of, for example, a non-volatile storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or flash memory.

[0029] The storage 13 stores the program 131. The program 131 includes computer-readable instructions for controlling the image forming apparatus 1. The program 131 includes the “discrimination program” in this disclosure. The processor 11 controls the various parts of the image forming apparatus 1 by executing the program 131 and realizes various processes according to this embodiment.

[0030] Program 131 may be provided not as a standalone program, but incorporated as part of any other program. In this case, processing according to this embodiment is realized in cooperation with the other program. Even if a program does not include such a partial module, it does not deviate from the spirit of the image forming apparatus 1 according to this embodiment. Furthermore, some or all of the functions provided by program 131 may be implemented by dedicated hardware.

[0031] The storage 13 further stores threshold information 132. The threshold information 132 includes thresholds for each of the multiple discrimination indicators used to determine the type of paper.

[0032] The paper feeding unit 15 holds multiple sheets of paper on which images will be formed. The paper feeding unit 15 supplies the paper to the image forming unit 30 one sheet at a time.

[0033] The media sensor 20 shines light onto the incoming paper and detects the light from the paper.

[0034] The image forming unit 30 applies toner to the conveyed paper to form an image. The image forming unit 30 includes an intermediate transfer belt 31, an image forming unit 32, and a transfer roller 33. The intermediate transfer belt 31 is stretched around a plurality of rollers and is configured to be rotatable. The image forming unit 32 is positioned along the intermediate transfer belt 31 and forms toner images of Y (yellow), M (magenta), C (cyan), and K (black) on the intermediate transfer belt 31 based on image data representing the image to be printed. As the paper passes through the nip formed between the intermediate transfer belt 31 and the transfer roller 33, the toner image is transferred to the paper and an image is formed.

[0035] The fuser unit 40 heats and pressurizes the paper onto which the toner image has been transferred to fix the toner image to the paper. The processor 11 determines the type of paper based on the information obtained from the media sensor 20 and changes the heating and pressurizing conditions of the fuser unit 40 according to the type of paper. The paper with the toner image fixed is discharged into the tray 83.

[0036] The control panel 50 includes an input unit 51 and a display unit 52. The input unit 51 receives user input and converts it into an operation signal, which is then output to the processor 11. The input unit 51 is, for example, a touch panel. The display unit 52 displays various information such as the operating status and processing results of the image forming apparatus 1. The display unit 52 is, for example, a liquid crystal display. In the control panel 50, the input unit 51 is arranged superimposed on the display unit 52.

[0037] The communication interface 60 transmits and receives information with the external device 500. For example, the processor 11 receives image data from the external device 500 via the communication interface 60.

[0038] Figure 3 shows an example of a media sensor in this embodiment. The media sensor 20 includes a light source unit 21, a light receiving sensor 22, substrates 23X, 23Y, and a reflector 24. The arrow AR shown in Figure 3 indicates the transport direction of the paper P supplied from the paper feeding unit 15 to the image forming unit 30.

[0039] The light source unit 21 includes light sources 211, 212, 213, 214, and 215. Light sources 211, 212, and 213 are reflective light sources. In the following description, when light sources 211, 212, and 213 are not distinguished, they will be referred to as "light source 21X". Light sources 214 and 215 are transmissive light sources. In the following description, when light sources 214 and 215 are not distinguished, they will be referred to as "light source 21Y". Both light sources 21X and 21Y are, for example, LEDs (Light-Emitting Diodes).

[0040] Light source 21X is mounted on substrate 23X. Light source 21X emits light in the wavelength range that is reflected by the surface of paper P. Light sources 211, 212, and 213 emit light of different wavelengths. Specifically, light source 211 emits light with a peak wavelength of 660 nm (hereinafter referred to as "660 nm light"). Light source 212 emits light with a peak wavelength of 940 nm (hereinafter referred to as "940 nm light"). Light source 213 emits light with a peak wavelength of 405 nm (hereinafter referred to as "405 nm light").

[0041] Light source 21Y is mounted on substrate 23Y. Light source 21Y emits light in a wavelength range that penetrates paper P. Light sources 214 and 215 emit light of different wavelengths. Specifically, light source 214 emits light with a peak wavelength of 460 nm (hereinafter referred to as "460 nm light"). Light source 215 emits light with a peak wavelength of 850 nm (hereinafter referred to as "850 nm light"). 850 nm light is an example of infrared light.

[0042] The light-receiving sensor 22 is, for example, a photodiode. The light-receiving sensor 22 is provided at a position on the optical path of the light irradiated from the light source 21X and reflected by the surface of the paper P, and also on the optical path of the light irradiated from the light source 21Y and transmitted through the paper P. As an example, the light-receiving sensor 22 is mounted on the substrate 23X. In the following description, the light irradiated from the light source 21X that is emitting light and reflected by the surface of the paper P is referred to as "reflected light", and the light irradiated from the light source 21Y that is emitting light and transmitted through the paper P is referred to as "transmitted light".

[0043] The light sources 211, 212, 213, 214, and 215 emit light in order at predetermined time intervals while the conveyed paper P is passing through. The light-receiving sensor 22 detects the reflected light and the transmitted light.

[0044] That is, by the light sources 211, 212, 213, 214, and 215 emitting light in order at predetermined time intervals while the conveyed paper P is passing through, the light-receiving sensor 22 detects the reflection amount of light at 660 nm, the reflection amount of light at 940 nm, the reflection amount of light at 405 nm, the transmission amount of light at 460 nm, and the transmission amount of light at 850 nm for the paper P.

[0045] The light-receiving sensor 22 outputs the detection information detected for the paper P to the processor 11. The detection information includes the reflection amount of light at 660 nm, the reflection amount of light at 940 nm, the reflection amount of light at 405 nm, the transmission amount of light at 460 nm, and the transmission amount of light at 850 nm.

[0046] <B. Outline of the processing of the image forming apparatus> Referring to FIG. 4, the outline of the processing of the image forming apparatus 1 in the present embodiment will be described.

[0047] Figure 4 is a diagram showing an overview of the processing of the image forming apparatus in this embodiment. The image forming apparatus 1 includes a light receiving sensor 22, an acquisition unit 151, a discrimination unit 152, a modification unit 153, a storage 13, and an operation panel 50. The acquisition unit 151, the discrimination unit 152, and the modification unit 153 are realized by the processor 11 executing program 131.

[0048] The acquisition unit 151 receives detection information from the light receiving sensor 22. The acquisition unit 151 acquires the measured values ​​of each of the multiple discrimination indicators used to determine the type of recording medium for the recording medium. Specifically, based on the detection information, the acquisition unit 151 calculates the measured values ​​of each of the multiple discrimination indicators used to determine the type of paper for the paper transported from the paper feeding unit 15.

[0049] The discrimination unit 152 determines the type of recording medium from among multiple recording medium types based on the comparison result between the measured value and the threshold for each of the multiple discrimination indicators. Specifically, the discrimination unit 152 determines the type of paper from plain paper, recycled paper, coated paper, and colored paper based on the comparison result between the measured value and the threshold for each of the multiple discrimination indicators. The threshold for each of the multiple discrimination indicators is set according to the IR transmittance, which is the infrared transmittance of the recording medium. The relationship between the threshold and the IR transmittance is expressed by a linear function. This speeds up the calculation processing by the processor 11 and reduces the amount of memory used. The thresholds are stored in the storage 13. Plain paper, recycled paper, coated paper, and colored paper are examples of the "multiple recording medium types" in this disclosure.

[0050] The input unit 51 receives an operation for inputting the type of the recording medium. When the determined type and the type input by the user are different, the changing unit 153 identifies a discrimination index to be the target of threshold change among a plurality of discrimination indexes so that the type of the recording medium is determined to be the input type, and changes the threshold of the target discrimination index. More specifically, when the paper type determined by the discrimination unit 152 and the paper type input by the user are different, the changing unit 153 identifies a discrimination index to be the target of threshold change among a plurality of discrimination indexes so that the type of the paper is determined to be the input paper type, and changes the threshold of the target discrimination index.

[0051] The changing unit 153 determines the amount of threshold change based on the difference between the measured value acquired by the acquisition unit 151 and the threshold corresponding to the IR transmittance of the recording medium. The changing unit 153 converts the difference between the measured value and the threshold corresponding to the IR transmittance of the recording medium into the number of steps based on a predetermined step unit, and determines the number of steps as the amount of change. By converting the amount of change into the number of steps based on a predetermined step unit, the arithmetic processing by the processor 11 can be accelerated and the memory to be used can be suppressed. The changing unit 153 changes the thresholds for each IR transmittance of the target discrimination index by the same amount in a lump sum.

[0052] When a plurality of thresholds are set for the target discrimination index, the changing unit 153 changes the plurality of thresholds by the same amount in a lump sum.

[0053] The display unit 52 displays the adjustment content by the changing unit 153. The adjustment content includes information indicating the target discrimination index and the amount of change of the threshold of the target discrimination index.

[0054] <C. Plurality of Discrimination Indexes> This section describes multiple discriminant indicators. Each of the multiple discriminant indicators is either the relative value of the transmittance of two types of light with different wavelengths, or the relative value of the reflectance of two types of light with different wavelengths. The relative value of the transmittance of two types of light with different wavelengths may be the difference between the transmittances of the two types of light with different wavelengths, or the ratio of the transmittances of the two types of light with different wavelengths. The relative value of the reflectance of two types of light with different wavelengths may be the difference between the reflectances of the two types of light with different wavelengths, or the ratio of the reflectances of the two types of light with different wavelengths.

[0055] Of the two types of light with different wavelengths, one has a wavelength that is highly sensitive to the object to be discriminated against (for example, a specific type of paper to be discriminated against), and the other has a wavelength that is less sensitive to the object to be discriminated against. The wavelength that is highly sensitive to the object to be discriminated against is the wavelength of light that the object to be discriminated against absorbs easily. On the other hand, the wavelength that is less sensitive to the object to be discriminated against is the wavelength of light that the object to be discriminated against does not absorb easily. By using the relative transmittance of the light with the wavelength that is highly sensitive to the object to be discriminated against and the light with the wavelength that is less sensitive to the object to be discriminated against, or the relative reflectance of the light with the wavelength that is highly sensitive to the object to be discriminated against and the light with the wavelength that is less sensitive to the object to be discriminated against, as each discriminant index, noise during detection by the light receiving sensor 22 (for example, the influence of individual differences in the light source, individual differences in the light receiving sensor 22, and / or the orientation of the paper, etc.) can be reduced. As a result, the accuracy of paper type discrimination is improved.

[0056] As the relative positional relationship between the light source, the light receiving sensor 22, and the paper changes depending on the orientation of the paper, the amount of transmitted light and reflected light detected by the light receiving sensor 22 also changes. To reduce the influence of the paper orientation, it is preferable that the paper orientation be as similar as possible when detecting each of the two types of light with different wavelengths. Therefore, it is preferable that the time difference in the detection timing of the two types of light with different wavelengths be as small as possible.

[0057] The threshold for each of the multiple discrimination indicators is set according to the IR transmittance, which is the infrared transmittance of the recording medium. IR transmittance is correlated with the basis weight of the paper. By setting the threshold for each of the multiple discrimination indicators according to the IR transmittance, the influence of the basis weight of the paper can be reduced. As a result, the accuracy of paper type discrimination is improved.

[0058] The transmittance is calculated using Equation 1 below, and the reflectance is calculated using Equation 2 below.

[0059] Transmittance=Tv / Ts...Formula 1

[0060] Reflectance=Rv / Rs...Formula 2

[0061] In Equation 1, "Tv" is the amount of light (transmitted light) emitted from the light source 21Y and transmitted through the paper P. In Equation 1, "Ts" is the amount of light detected by the light receiving sensor 22 when the light source 21Y is emitted while no paper is in the optical path of the light source 21Y. The value of "Ts" in Equation 1 is predetermined by measurement. The value of "Ts" may also be measured when the processor 11 receives a paper type identification instruction.

[0062] In Equation 2, "Rv" is the amount of light (reflected light) that is irradiated from the light source 21X and reflected from the surface of the paper P. In Equation 2, "Rs" is the amount of light that is irradiated from the light source 21X when there is no paper in the optical path of the light source 21X and reflected from the surface of the reflector 24. The value of "Rs" in Equation 2 is predetermined by measurement. The value of "Rs" may also be measured when the processor 11 receives a paper type identification instruction.

[0063] The acquisition unit 151 uses the detection information about the paper P received from the light receiving sensor 22 and Equation 1 to calculate the transmittance of 460 nm light and the transmittance of 850 nm light (IR transmittance). The acquisition unit 151 uses the detection information about the paper P received from the light receiving sensor 22 and Equation 2 to calculate the reflectance of 660 nm light, the reflectance of 940 nm light and the reflectance of 405 nm light.

[0064] In this embodiment, a first colored paper discrimination index (hereinafter referred to as "colored paper discrimination index A1"), a second colored paper discrimination index (hereinafter referred to as "colored paper discrimination index A2"), a coated paper discrimination index, and a recycled paper pulp discrimination index are used as multiple discrimination indicators.

[0065] Figure 5 shows an example of a graph of the colored paper discrimination index A1 in this embodiment. The colored paper discrimination index A1 is an index for discriminating colored paper. The colored paper discrimination index A1 is the ratio of the transmittance of two types of light with different wavelengths. Specifically, the colored paper discrimination index A1 is the ratio of the transmittance of 460 nm light to the transmittance of 850 nm light. 460 nm light is an example of light with a wavelength that is highly sensitive to yellow-toned colored paper. That is, if a certain paper absorbs a lot of 460 nm light, then that paper is yellow-toned colored paper. If a certain paper is yellow-toned colored paper, the darker the color of the paper, the more 460 nm light it absorbs. 850 nm light is an example of light with a wavelength that is less sensitive to yellow-toned colored paper.

[0066] The threshold for the colored paper discrimination index A1 is set according to the transmittance of 850nm light, i.e., the IR transmittance.

[0067] In the graph of the colored paper discrimination index A1 shown in Figure 5, the horizontal axis represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis represents the ratio of the transmittance of light at 460 nm to the transmittance of light at 850 nm. Reference lines LA11 and LA12 in Figure 5 indicate the threshold values ​​for the colored paper discrimination index A1. Reference line LA11 in Figure 5 indicates the threshold value for colored paper discrimination index A1 when the IR transmittance is low (when the basis weight is high), and reference line LA12 in Figure 5 indicates the threshold value for colored paper discrimination index A1 when the IR transmittance is high (when the basis weight is low). Even with a single discrimination index, the influence of basis weight can be reduced by changing the slope of the reference line that indicates the threshold value depending on the basis weight.

[0068] The acquisition unit 151 calculates the measured value of the color paper discrimination index A1 for the paper P using the following formula 3.

[0069] Measured value of colored paper discrimination index A1 = (transmittance of light at 460nm) / (transmittance of light at 850nm) ... Equation 3

[0070] If the measured value in the colored paper discrimination index A1 is less than the threshold corresponding to the IR transmittance of the paper P, the discrimination unit 152 determines that the type of paper P is colored paper.

[0071] Figure 6 shows an example of a graph of the colored paper discrimination index A2 in this embodiment. The colored paper discrimination index A2 is an index for discriminating cyan (light blue) colored paper. The colored paper discrimination index A2 is the ratio of the reflectances of two types of light with different wavelengths. Specifically, the colored paper discrimination index A2 is the ratio of the reflectance of 660 nm light to the reflectance of 940 nm light. 660 nm light is an example of light with a wavelength that is highly sensitive to cyan colored paper. That is, if a certain paper absorbs a lot of 660 nm light, then that paper is cyan colored paper. If a certain paper is cyan colored paper, the darker the color of the paper, the more 660 nm light it absorbs. 940 nm light is an example of light with a wavelength that is less sensitive to cyan colored paper.

[0072] The threshold for the colored paper discrimination index A2 is set according to the transmittance of 850nm light, i.e., the IR transmittance.

[0073] In the graph of the colored paper discrimination index A2 shown in Figure 6, the horizontal axis represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis represents the ratio of the reflectance of light at 660 nm to the reflectance of light at 940 nm. The reference line LA2 in Figure 6 indicates the threshold value of the colored paper discrimination index A2.

[0074] The acquisition unit 151 calculates the measured value of the color paper discrimination index A2 for the paper P using the following formula 4.

[0075] The measured value of the colored paper discrimination index A2 = (reflectance of light at 660nm) / (reflectance of light at 940nm) ... Equation 4

[0076] If the measured value in the colored paper discrimination index A2 is less than the threshold corresponding to the IR transmittance of the paper P, the discrimination unit 152 determines that the type of paper P is colored paper.

[0077] Figure 7 shows an example of a graph of the coated paper discrimination index in this embodiment. The coated paper discrimination index is an index for distinguishing coated paper. The coated paper discrimination index is the difference in transmittance between two types of light with different wavelengths. Specifically, the coated paper discrimination index is the difference between the transmittance of 850 nm light and the transmittance of 460 nm light. 460 nm light is an example of light with a wavelength that is highly sensitive to coated paper. 850 nm light is an example of light with a wavelength that is less sensitive to coated paper.

[0078] The threshold for the coated paper discrimination index is set according to the transmittance of light at 850 nm, i.e., the IR transmittance.

[0079] In the graph of the coated paper discrimination index shown in Figure 7, the horizontal axis represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis represents the difference between the transmittance of light at 850 nm and the transmittance of light at 460 nm. The reference lines LB1 and LB2 in Figure 7 indicate the thresholds for the coated paper discrimination index. Specifically, reference line LB1 in Figure 7 indicates the threshold for distinguishing between coated paper and non-coated paper in the coated paper discrimination index. Reference line LB2 in Figure 7 indicates the threshold for distinguishing between coated paper with a thin coating layer and coated paper with a thick coating layer in the coated paper discrimination index. In the following explanation, the threshold for distinguishing between coated paper and non-coated paper in the coated paper discrimination index will be referred to as the "first threshold." In the following explanation, the threshold for distinguishing between coated paper with a thin coating layer and coated paper with a thick coating layer in the coated paper discrimination index will be referred to as the "second threshold." Multiple thresholds are set for the coated paper discrimination index.

[0080] The acquisition unit 151 calculates the measured value of the coated paper discrimination index for the paper P using the following formula 5.

[0081] Coated paper discrimination index measurement value = (transmittance of light at 850nm) - (transmittance of light at 460nm) ... Equation 5

[0082] If the measured value in the coated paper discrimination index is less than the first threshold corresponding to the IR transmittance of the paper P, the discrimination unit 152 determines that the type of paper P is something other than coated paper (for example, plain paper).

[0083] Figure 8 shows an example of a graph of the recycled paper pulp discrimination index in this embodiment. The recycled paper pulp discrimination index is an index for distinguishing recycled paper pulp. The recycled paper pulp discrimination index is the ratio of the reflectances of two types of light with different wavelengths. Specifically, the recycled paper pulp discrimination index is the ratio of the reflectance of 405 nm light to the reflectance of 940 nm light.

[0084] Light at 405 nm is an example of light with a wavelength that is highly sensitive to recycled paper. Light at 940 nm is an example of light with a wavelength that is less sensitive to recycled paper. Recycled pulp contains more impurities than virgin pulp. These impurities absorb a lot of 405 nm light but hardly any 940 nm light. Therefore, if paper contains a lot of recycled pulp, the ratio of the reflectance of 405 nm light to the reflectance of 940 nm light will be small.

[0085] The threshold for the recycled paper pulp identification index is set according to the transmittance of light at 850 nm, i.e., the IR transmittance.

[0086] In the graph of the recycled paper pulp discrimination index shown in Figure 8, the horizontal axis represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis represents the ratio of the reflectance of light at 405 nm to the reflectance of light at 940 nm. The reference line LC in Figure 8 indicates the threshold value of the recycled paper pulp discrimination index.

[0087] The acquisition unit 151 calculates the measured value of the recycled pulp discrimination index for the paper P using the following formula 6.

[0088] The measured value of the recycled paper pulp identification index = (reflectance of light at 405 nm) / (reflectance of light at 940 nm) ... Equation 6

[0089] If the measured value in the recycled paper pulp discrimination index is greater than or equal to the threshold corresponding to the IR transmittance of the paper P, the discrimination unit 152 determines that the type of paper P is something other than recycled paper.

[0090] Figure 9 shows the paper types that can be determined by the combination of the colored paper discrimination index, coated paper discrimination index, and recycled paper pulp discrimination index in this embodiment. If the measured value of at least one of the multiple colored paper discrimination indexes indicates colored paper (for example, if the measured value of at least one of the multiple colored paper discrimination indexes is below the threshold), the discrimination unit 152 determines that the type of recording medium is colored paper. If none of the measured values ​​of the multiple colored paper discrimination indexes indicate colored paper (for example, if the measured value of any of the multiple colored paper discrimination indexes is above the threshold), the discrimination unit 152 determines that the type of recording medium is something other than colored paper.

[0091] More specifically, if the measured value of at least one of the colored paper discrimination index A1 and colored paper discrimination index A2 is below the threshold, the discrimination unit 152 determines that the type of paper P is colored paper.

[0092] If the measured value for both colored paper discrimination index A1 and colored paper discrimination index A2 is above the threshold, and the measured value for coated paper discrimination index is below the first threshold, the discrimination unit 152 determines that the type of paper P is plain paper.

[0093] If the measured value for both colored paper discrimination index A1 and colored paper discrimination index A2 is above the threshold, and the measured value for coated paper discrimination index is above the first threshold, and the measured value for recycled pulp discrimination index is above the threshold, the discrimination unit 152 determines that the type of paper P is coated paper.

[0094] If the measured value for both colored paper discrimination index A1 and colored paper discrimination index A2 is above the threshold, and the measured value for coated paper discrimination index is above the first threshold, and the measured value for recycled pulp discrimination index is below the threshold, the discrimination unit 152 determines that the type of paper P is recycled paper.

[0095] Furthermore, if the type of paper P is determined to be coated paper, and the measured value in the coated paper discrimination index is greater than or equal to the first threshold but less than the second threshold, the discrimination unit 152 may further determine that the type of paper P is coated paper with a thin coating layer. If the type of paper P is determined to be coated paper, and the measured value in the coated paper discrimination index is greater than or equal to the second threshold, the discrimination unit 152 may further determine that the type of paper P is coated paper with a thick coating layer.

[0096] Figure 10 shows candidate discrimination indicators for which the threshold value is changed in this embodiment. Candidate discrimination indicators for the target are the shaded discrimination indicators. In Figure 10, "A" represents the colored paper discrimination indicator, "B" represents the coated paper discrimination indicator, and "C" represents the recycled paper pulp discrimination indicator.

[0097] For example, if the type entered for a certain paper is plain paper, and the type identified for that paper is coated paper, the threshold for the coated paper discrimination index is raised, and if the measured value falls below the first threshold, the paper is identified as plain paper. Therefore, if the entered type is plain paper and the identified type is coated paper, the candidate for the discrimination index is the coated paper discrimination index.

[0098] Similarly, if the input type is plain paper and the identified type is recycled paper, the candidate for the identification index is the coated paper identification index. If the input type is plain paper and the identified type is colored paper, the candidate for the identification index is both the colored paper identification index and the coated paper identification index.

[0099] When the input type is coated paper and the discriminated type is plain paper, the candidates for the discrimination index of the target are the coated paper discrimination index and the waste pulp discrimination index. When the input type is coated paper and the discriminated type is recycled paper, the candidates for the discrimination index of the target are the waste pulp discrimination index. When the input type is coated paper and the discriminated type is colored paper, the candidates for the discrimination index of the target are the colored paper discrimination index, the coated paper discrimination index, and the waste pulp discrimination index.

[0100] When the input type is recycled paper and the discriminated type is plain paper, the candidates for the discrimination index of the target are the coated paper discrimination index and the waste pulp discrimination index. When the input type is recycled paper and the discriminated type is coated paper, the candidates for the discrimination index of the target are the waste pulp discrimination index. When the input type is recycled paper and the discriminated type is colored paper, the candidates for the discrimination index of the target are the colored paper discrimination index, the coated paper discrimination index, and the waste pulp discrimination index.

[0101] When the input type is colored paper and the discriminated type is plain paper, coated paper, or recycled paper, the candidates for the discrimination index of the target are the colored paper discrimination index.

[0102] When there is one candidate for the discrimination index of the target, the change unit 153 changes the threshold value of the candidate. On the other hand, when there are multiple candidates for the discrimination index of the target, the change unit 153 changes the threshold value of the candidate among the multiple candidates for which the magnitude relationship between the measured value and the threshold value for the paper to be discriminated is different from the magnitude relationship between the measured value and the threshold value for the input type.

[0103] <D. Procedure of adjustment processing> Referring to FIGS. 11 to 16, the procedure of the adjustment processing will be described. The adjustment processing is a process of specifying a discrimination index for which the threshold value is to be changed among a plurality of discrimination indexes so that the type of the recording medium is discriminated as the input type when the discriminated type and the input type of the recording medium are different, and changing the threshold value of the discrimination index of the target. In the present embodiment, the adjustment processing is executed in the paper type automatic adjustment mode.

[0104] Figure 11 is a flowchart showing part of the adjustment process procedure in this embodiment. Figure 12 is a flowchart showing the remaining part of the adjustment process procedure in this embodiment.

[0105] In step S1, the processor 11 receives an instruction to start the adjustment process. Now, with reference to Figure 13, the method for inputting the instruction to start the adjustment process will be described. Figure 13 is a diagram showing an example of a screen for receiving an operation to instruct the start of the adjustment process in this embodiment.

[0106] Screen G1 is an example of a screen that accepts an operation to instruct the start of the adjustment process. Screen G1 is displayed on the display unit 52. Screen G1 includes buttons B1 and B2 for the user to input the instruction to start the adjustment process. If the user presses button B1 and then button B2, the processor 11 accepts the instruction to start the adjustment process. When the processor 11 accepts the instruction to start the adjustment process, it instructs the display unit 52 to switch from screen G1 to screen G2.

[0107] Referring again to Figure 11, in step S2, the processor 11 accepts the type of recording medium (for example, paper type). Now, referring to Figure 14, the method for inputting the type of recording medium will be described. Figure 14 is a diagram showing an example of a screen that accepts the operation to input the type of recording medium in this embodiment.

[0108] Screen G2 is an example of a screen that accepts input for the type of recording medium. Screen G2 is a screen for selecting the type of recording medium from among several types of recording media. Screen G2 is displayed on the display unit 52. Screen G2 includes buttons B3 corresponding to each of the multiple types of recording media and a button B4 for confirming the selection operation. If the user presses button B4 after pressing button B3 corresponding to the type of recording media, the processor 11 accepts the type corresponding to button B3 pressed by the user as the type of recording media. Since the user only needs to select the type of recording media from among several types of recording media, user operability is improved.

[0109] Furthermore, screen G2 is not limited to a screen for selecting the type of recording medium from multiple types. Screen G2 may also be a screen for manually entering the type of recording medium.

[0110] Referring again to Figure 11, in step S3, the processor 11 outputs a light emission instruction to the light source unit 21.

[0111] In step S4, the processor 11 receives detection information detected by the light receiving sensor 22 from the light receiving sensor 22.

[0112] In step S5, the processor 11 obtains the measured values ​​of each of the multiple discrimination indicators for the recording medium.

[0113] In step S6, the processor 11 determines the type of recording medium from among multiple recording medium types based on the comparison result between the measured value and the threshold for each of the multiple discrimination indicators.

[0114] Referring to Figure 12, in step S7, the processor 11 determines whether the identified type and the input type are different. The identified type is the type identified in step S6. The input type is the type received in step S2. If the identified type and the input type are different (YES in step S7), the processor 11 proceeds to step S8. On the other hand, if the identified type and the input type are the same (NO in step S7), the processor 11 proceeds to step S12.

[0115] In step S8, the processor 11 identifies a discrimination indicator from among several discrimination indicators whose threshold should be changed so that the type of recording medium is determined to be the type that was input.

[0116] In step S9, the processor 11 determines the amount to change the threshold of the target discrimination index so that the type of recording medium is determined to be the type that was input. More specifically, the processor 11 converts the difference between the measurement value obtained in step S5 and the threshold corresponding to the IR transmittance of the recording medium into a number of steps based on a predetermined step unit, and determines this number of steps as the amount of change.

[0117] In step S10, the processor 11 changes the threshold of the target discrimination index by the amount determined in step S9.

[0118] In step S11, the processor 11 instructs the display unit 52 to display a screen showing the adjustment details. The screen showing the adjustment details will now be described with reference to Figure 15. Figure 15 is a diagram showing an example of the screen showing the adjustment details in this embodiment.

[0119] Screen G3 is an example of a screen showing adjustment details. Screen G3 is displayed on the display unit 52. Screen G3 includes information m1 indicating the input type, information m2 indicating the determined type, and information m3 indicating the adjustment details. Information m3 indicates the target discrimination index and the amount of change in the threshold of the target discrimination index. Screen G3 further includes information m4 indicating the type of recording medium that will be determined when the threshold of the target discrimination index is changed according to the adjustment details shown in information m3. The type shown by information m4 matches the type shown by information m1.

[0120] The user can see what adjustments have been made through screen G3. Note that step S11 may be executed after step S9 and before step S10. That is, after step S9, the processor 11 may instruct the display unit 52 to display screen G3, and then execute step S10 in response to button B5 on screen G3 being pressed.

[0121] Referring again to Figure 12, in step S12, the processor 11 instructs the display unit 52 to display a screen indicating that no adjustment was performed. Now, referring to Figure 16, the screen indicating that no adjustment was performed will be described. Figure 16 is a diagram showing an example of the screen indicating that no adjustment was performed in this embodiment.

[0122] Screen G4 is an example of a screen indicating that no adjustment was made. Screen G4 is displayed on the display unit 52. Screen G4 includes information m1 indicating the input type and information m2 indicating the determined type. Screen G4 further includes information m5 indicating that the threshold was not changed for any of the multiple discrimination indicators because the determined type and the input type were the same. Screen G4 allows the user to know that the threshold was not changed for any of the multiple discrimination indicators.

[0123] Referring again to Figure 12, the adjustment process is completed after step S11 or step S12.

[0124] <E. Examples 1 to 4> (E1: Overview) Referring to FIGS. 17 to 31, four specific examples (Examples 1 to 4) of the adjustment process will be described. In Example 1, for the paper whose type is to be discriminated (hereinafter referred to as "the paper to be discriminated"), the adjustment process when the discriminated type is coated paper and the input type is plain paper will be described. In Example 2, for the paper to be discriminated, the adjustment process when the discriminated type is plain paper and the input type is recycled paper will be described. In Example 3, for the paper to be discriminated, the adjustment process when the discriminated type is colored paper and the input type is coated paper will be described. In Example 4, for the paper to be discriminated, the adjustment process when the discriminated type is recycled paper and the input type is colored paper will be described.

[0125] FIG. 17 is a diagram showing the measured values of each discrimination index for the paper to be discriminated in Examples 1 to 4, the threshold value corresponding to the IR transmittance of the paper to be discriminated, and the difference between the measured value and the threshold value. "Transmittance difference 850 - 460" in FIG. 17 indicates the measured value of the coated paper discrimination index for the paper to be discriminated. "Transmittance ratio 460 / 850" in FIG. 17 indicates the measured value of the colored paper discrimination index A1 for the paper to be discriminated. "Reflectance ratio 405 / 940" in FIG. 17 indicates the measured value of the waste pulp discrimination index for the paper to be discriminated. "Reflectance ratio 660 / 940" in FIG. 17 indicates the measured value of the colored paper discrimination index A2 for the paper to be discriminated.

[0126] The "y-coordinate of the plot position of the measured value" in FIG. 17 means the y-coordinate of the point indicating the measured value for the paper to be discriminated in each of the graphs of the discrimination indices shown in FIGS. 18 to 21.

[0127] The "y-coordinate of the plot position of the threshold value" in FIG. 17 means the y-coordinate of the point indicating the threshold value (in the case of the coated paper discrimination index, the first threshold value corresponding to the IR transmittance of the paper to be discriminated) corresponding to the IR transmittance of the paper to be discriminated in each of the graphs of the discrimination indices shown in FIGS. 18 to 21.

[0128] In Figure 17, "difference" refers to the difference between the y-coordinate value of the point representing the measured value for the paper being discriminated in each of the discrimination index graphs shown in Figures 18 to 21, and the y-coordinate value of the point representing the threshold corresponding to the IR transmittance of the paper being discriminated (in the case of the coated paper discrimination index, the first threshold corresponding to the IR transmittance of the paper being discriminated).

[0129] When the points representing the measured values ​​shown in Figure 17 are plotted on the graphs of each discrimination index, the results are as shown in Figures 18 to 21. Figure 18 is a graph showing the relationship between the measured values ​​of the colored paper discrimination index A1 for the paper to be discriminated against in Examples 1 to 4 and the threshold corresponding to the IR transmittance of the paper to be discriminated against. Figure 19 is a graph showing the relationship between the measured values ​​of the colored paper discrimination index A2 for the paper to be discriminated against in Examples 1 to 4 and the threshold corresponding to the IR transmittance of the paper to be discriminated against. Figure 20 is a graph showing the relationship between the measured values ​​of the coated paper discrimination index for the paper to be discriminated against in Examples 1 to 4 and the threshold corresponding to the IR transmittance of the paper to be discriminated against. Figure 21 is a graph showing the relationship between the measured values ​​of the recycled pulp discrimination index for the paper to be discriminated against in Examples 1 to 4 and the threshold corresponding to the IR transmittance of the paper to be discriminated against. In Figures 18 to 21, the diamond marks represent points representing the measured values ​​in Example 1, the square marks represent points representing the measured values ​​in Example 2, the triangle marks represent points representing the measured values ​​in Example 3, and the cross marks represent points representing the measured values ​​in Example 4.

[0130] In the graph of the colored paper discrimination index A1 shown in Figure 18, the horizontal axis (X-axis) represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis (Y-axis) represents the ratio of the transmittance of light at 460 nm to the transmittance of light at 850 nm. Reference lines LA11 and LA12 in Figure 18 indicate the threshold values ​​of the colored paper discrimination index A1.

[0131] In the graph of the colored paper discrimination index A2 shown in Figure 19, the horizontal axis (X-axis) represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis (Y-axis) represents the ratio of the reflectance of light at 660 nm to the reflectance of light at 940 nm. The reference line LA2 in Figure 19 indicates the threshold value of the colored paper discrimination index A2.

[0132] In the coated paper discrimination index graph shown in Figure 20, the horizontal axis (X-axis) represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis (Y-axis) represents the difference between the transmittance of light at 850 nm and the transmittance of light at 460 nm. Reference lines LB1 and LB2 in Figure 20 indicate the thresholds for the coated paper discrimination index. Reference line LB1 in Figure 20 indicates the first threshold for distinguishing between coated paper and non-coated paper in the coated paper discrimination index. Reference line LB2 in Figure 20 indicates the second threshold for distinguishing between coated paper with a thin coating layer and coated paper with a thick coating layer in the coated paper discrimination index. Multiple thresholds are set for the coated paper discrimination index.

[0133] In the graph of the recycled paper pulp discrimination index shown in Figure 21, the horizontal axis (X-axis) represents the transmittance of light at 850 nm (IR transmittance), and the vertical axis (Y-axis) represents the ratio of the reflectance of light at 405 nm to the reflectance of light at 940 nm. The reference line LC in Figure 21 indicates the threshold value of the recycled paper pulp discrimination index.

[0134] Figure 22 shows the slope and intercept of the reference lines for each discrimination index in Examples 1 to 4. The first reference line for colored paper discrimination index A1 in Figure 22 is reference line LA11 in Figure 18. The second reference line for colored paper discrimination index A1 in Figure 22 is reference line LA12 in Figure 18. The reference line for colored paper discrimination index A2 in Figure 22 is reference line LA2 in Figure 19.

[0135] The first reference line for the coated paper discrimination index in Figure 22 is reference line LB1 in Figure 20. The second reference line for the coated paper discrimination index in Figure 22 is reference line LB2 in Figure 20. The reference line for the recycled pulp discrimination index in Figure 22 is reference line LC in Figure 21. The slope and intercept of each reference line are as shown in Figure 22. As shown in Figures 18 to 22, the relationship between the threshold and IR transmittance is expressed by a linear function.

[0136] Figure 23 shows the step units used when determining the threshold change amount in Examples 1 to 4. One step of the colored paper discrimination index A1 and colored paper discrimination index A2 is 0.03. One step of the coated paper discrimination index is 0.01. One step of the recycled pulp discrimination index is 0.03. Figure 24 shows the threshold change amount in Examples 1 to 4.

[0137] (E2: Example 1) The adjustment process for Example 1 will now be described. In Example 1, the type of paper to be identified is coated paper, and the type entered is plain paper.

[0138] Referring to Figures 17 to 21, in Example 1, the measured values ​​for the paper to be identified are equal to or greater than the threshold corresponding to the IR transmittance of the paper to be identified (in the case of the coated paper identification index, the first threshold corresponding to the IR transmittance of the paper to be identified) for all of the colored paper identification index A1, colored paper identification index A2, coated paper identification index, and recycled paper pulp identification index. As shown in Figure 9, the paper type for which the measured values ​​are equal to or greater than the threshold (in the case of the coated paper identification index, the first threshold) for all of the colored paper identification index A1, colored paper identification index A2, coated paper identification index, and recycled paper pulp identification index is coated paper. Therefore, the identification unit 152 identifies the type of paper to be identified as coated paper.

[0139] On the other hand, the type entered by the user is plain paper. The type identified and the type entered are different. Referring to Figure 10, if the identified type is coated paper and the type entered is plain paper, the modification unit 153 identifies the coated paper identification index as the identification index for the target. Referring to Figure 17, in the coated paper identification index, the difference between the measured value for the paper to be identified and the first threshold corresponding to the IR transmittance of the paper to be identified is +0.028.

[0140] For the discrimination unit 152 to determine that the paper to be discriminated against is plain paper, the measured value for the paper to be discriminated against in the coated paper discrimination index must be less than the first threshold (see Figure 9). In other words, for the discrimination unit 152 to determine that the paper to be discriminated against is plain paper, the point indicating the measured value for the paper to be discriminated against in the coated paper discrimination index graph shown in Figure 20 (the point indicated by the diamond mark in Figure 20) must be located below the reference line LB1. However, currently, in the coated paper discrimination index graph shown in Figure 20, the point indicating the measured value for the paper to be discriminated against (the point indicated by the diamond mark in Figure 20) is located above the reference line LB1. Therefore, the modification unit 153 adjusts the threshold for the coated paper discrimination index.

[0141] Referring to Figure 23, the step unit of the coated paper discrimination index is 0.01. The modification unit 153 converts the difference between the measured value for the paper to be discriminated in the coated paper discrimination index and the first threshold corresponding to the IR transmittance of the paper to be discriminated (in Example 1, +0.028) to the smallest number of steps greater than or equal to the difference (i.e., +3 steps) (see Figure 24). The modification unit 153 raises the threshold for each IR transmittance of the coated paper discrimination index by 3 steps all at once. Since multiple thresholds (a first threshold indicated by the reference line LB1 and a second threshold indicated by the reference line LB2) are set for the coated paper discrimination index, the modification unit 153 raises these multiple thresholds by 3 steps all at once.

[0142] As a result, in the coated paper discrimination index graph shown in Figure 20, the reference lines LB1 and LB2 move upward by 3 steps. Figure 25 shows the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph before and after the adjustment process for Example 1. The solid lines in Figure 25 show the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph before the adjustment process. The dotted lines in Figure 25 show the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph after the adjustment process. As shown in Figure 25, the threshold adjustment by the modification unit 153 moves the reference lines LB1 and LB2 from the positions shown by the solid lines to the positions shown by the dotted lines. As a result, after the adjustment, in the coated paper discrimination index graph, the point indicating the measured value for the paper to be discriminated (the point indicated by the diamond mark in Figure 25) is located below the reference line LB1. That is, after the adjustment process, in the coated paper discrimination index, the measured value for the paper to be discriminated is less than the first threshold.

[0143] As shown in Figure 24, in Example 1, the threshold for the coated paper discrimination index is raised by three steps all at once. Therefore, if the discrimination unit 152 performs type discrimination on the paper to be discriminated against again after the adjustment process, the paper to be discriminated against will be identified as plain paper, which is the type entered by the user.

[0144] Furthermore, since each of the multiple thresholds in the coated paper discrimination index (the first threshold indicated by the reference line LB1, and the second threshold indicated by the reference line LB2) is changed by the same amount all at once, the relationship between the multiple thresholds (the first threshold indicated by the reference line LB1 < the second threshold indicated by the reference line LB2) is maintained.

[0145] (E3: Example 2) The adjustment process for Example 2 will now be described. In Example 2, the type of paper to be identified is plain paper, and the type entered is recycled paper.

[0146] Referring to Figures 17 to 21, in Example 2, the measured values ​​for the paper to be identified in the colored paper identification index A1, colored paper identification index A2, and recycled pulp identification index are above the threshold corresponding to the IR transmittance of the paper to be identified. On the other hand, in Example 2, the measured value for the paper to be identified in the coated paper identification index is below the first threshold corresponding to the IR transmittance of the paper to be identified. As shown in Figure 9, the paper type in which the measured values ​​for colored paper identification index A1, colored paper identification index A2, and recycled pulp identification index are above the threshold, and the measured value for the coated paper identification index is below the first threshold, is plain paper. Therefore, the identification unit 152 identifies the type of paper to be identified as plain paper.

[0147] On the other hand, the type entered by the user is recycled paper. The type identified and the type entered are different. Referring to Figure 10, if the identified type is plain paper and the type entered is recycled paper, the modification unit 153 identifies the coated paper identification index and the recycled pulp identification index as candidate identification indexes for the target.

[0148] First, the modification unit 153 determines whether or not the threshold needs to be adjusted for the coated paper discrimination index among the candidate discrimination indexes for the target. Referring to Figure 17, in the coated paper discrimination index, the difference between the measured value for the paper to be discriminated against and the first threshold corresponding to the IR transmittance of the paper to be discriminated against is -0.019. For the discrimination unit 152 to discriminate that the paper to be discriminated against is recycled paper, the measured value for the paper to be discriminated against in the coated paper discrimination index must be equal to or greater than the first threshold (see Figure 9).

[0149] In other words, for the discrimination unit 152 to determine that the paper to be discriminated is recycled paper, the point indicating the measured value for the paper to be discriminated (indicated by the square mark in Figure 20) must be located on or above the reference line LB1 in the coated paper discrimination index graph shown in Figure 20. However, currently, in the coated paper discrimination index graph shown in Figure 20, the point indicating the measured value for the paper to be discriminated (indicated by the square mark in Figure 20) is located below the reference line LB1. Therefore, the modification unit 153 determines that the threshold of the coated paper discrimination index among the candidate discrimination indexes for the target needs to be adjusted, and identifies the coated paper discrimination index as the discrimination index for the target.

[0150] Referring to Figure 23, the step unit of the coated paper discrimination index is 0.01. The modification unit 153 converts the difference between the measured value for the paper to be discriminated in the coated paper discrimination index and the first threshold corresponding to the IR transmittance of the paper to be discriminated (in Example 2, -0.019) to the smallest number of steps greater than or equal to the difference (i.e., -2 steps) (see Figure 24). The modification unit 153 lowers the threshold for each IR transmittance of the coated paper discrimination index by 2 steps at once. Since multiple thresholds (a first threshold indicated by the reference line LB1 and a second threshold indicated by the reference line LB2) are set for the coated paper discrimination index, the modification unit 153 lowers these multiple thresholds by 2 steps at once.

[0151] As a result, in the coated paper discrimination index graph shown in Figure 20, the reference lines LB1 and LB2 move downward by two steps. Figure 26 shows the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph before and after the adjustment process for Example 2. The solid lines in Figure 26 show the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph before the adjustment process. The dotted lines in Figure 26 show the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph after the adjustment process. As shown in Figure 26, the threshold adjustment by the modification unit 153 moves the reference lines LB1 and LB2 from the positions shown by the solid lines to the positions shown by the dotted lines. As a result, after the adjustment, in the coated paper discrimination index graph, the point indicating the measured value for the paper to be discriminated (the point indicated by the square mark in Figure 26) is located above the reference line LB1. That is, after the adjustment process, in the coated paper discrimination index, the measured value for the paper to be discriminated is greater than or equal to the first threshold.

[0152] Next, the modification unit 153 determines whether or not the threshold of the recycled pulp discrimination index among the candidate discrimination indexes for the target needs to be adjusted. Referring to Figure 17, in the recycled pulp discrimination index, the difference between the measured value for the paper to be discriminated against and the threshold corresponding to the IR transmittance of the paper to be discriminated against is +0.020. For the discrimination unit 152 to discriminate that the paper to be discriminated against is recycled paper, the measured value for the paper to be discriminated against in the recycled pulp discrimination index must be less than the threshold (see Figure 9).

[0153] In other words, for the discrimination unit 152 to determine that the paper to be discriminated against is recycled paper, the point indicating the measured value for the paper to be discriminated against (indicated by the square mark in Figure 21) must be located below the baseline LC in the graph of the recycled paper pulp discrimination index shown in Figure 21. However, currently, in the graph of the recycled paper pulp discrimination index shown in Figure 21, the point indicating the measured value for the paper to be discriminated against (indicated by the square mark in Figure 21) is located above the baseline LC. Therefore, the modification unit 153 determines that the threshold of the recycled paper pulp discrimination index among the candidate discrimination indexes for the target needs to be adjusted, and identifies the recycled paper pulp discrimination index as the discrimination index for the target.

[0154] Referring to Figure 23, the step unit of the recycled pulp discrimination index is 0.03. The modification unit 153 converts the difference between the measured value for the paper to be discriminated in the recycled pulp discrimination index and the threshold corresponding to the IR transmittance of the paper to be discriminated (in Example 2, +0.020) to the smallest step number that is greater than or equal to the difference (i.e., +1 step) (see Figure 24). The modification unit 153 raises the threshold for each IR transmittance of the recycled pulp discrimination index by 1 step all at once.

[0155] As a result, the baseline LC in the recycled pulp discrimination index graph shown in Figure 21 moves upward by one step. Figure 27 shows the position of the baseline LC in the recycled pulp discrimination index graph before and after the adjustment process for Example 2. The solid line in Figure 27 shows the position of the baseline LC in the recycled pulp discrimination index graph before the adjustment process. The dotted line in Figure 27 shows the position of the baseline LC in the recycled pulp discrimination index graph after the adjustment process. As shown in Figure 27, the threshold adjustment by the modification unit 153 moves the baseline LC from the position shown by the solid line to the position shown by the dotted line. As a result, after the adjustment, in the recycled pulp discrimination index graph, the point indicating the measured value for the paper to be discriminated (the point indicated by the square mark in Figure 27) is located below the baseline LC. That is, after the adjustment process, the measured value for the paper to be discriminated in the recycled pulp discrimination index is below the threshold.

[0156] As shown in Figure 24, in Example 2, the threshold for the coated paper discrimination index is lowered by two steps collectively, and the threshold for the recycled pulp discrimination index is raised by one step collectively. Therefore, if the discrimination unit 152 performs type discrimination on the paper to be discriminated against again after the adjustment process, the paper to be discriminated against will be identified as recycled paper, which is the type entered by the user.

[0157] Furthermore, since each of the multiple thresholds in the coated paper discrimination index (the first threshold indicated by the reference line LB1, and the second threshold indicated by the reference line LB2) is changed by the same amount all at once, the relationship between the multiple thresholds (the first threshold indicated by the reference line LB1 < the second threshold indicated by the reference line LB2) is maintained.

[0158] (E4: Example 3) The adjustment process for Example 3 will now be described. In Example 3, the type of paper to be identified is colored paper, and the type entered is coated paper.

[0159] Referring to Figures 17 to 21, in Example 3, the measured values ​​for the paper to be identified in the colored paper identification index A1 and the recycled pulp identification index are equal to or greater than the threshold corresponding to the IR transmittance of the paper to be identified. On the other hand, in Example 3, the measured values ​​for the paper to be identified in the colored paper identification index A2 and the coated paper identification index are less than the threshold corresponding to the IR transmittance of the paper to be identified (in the case of the coated paper identification index, the first threshold corresponding to the IR transmittance of the paper to be identified). As explained with reference to Figure 9, if the measured value in at least one of the colored paper identification index A1 and colored paper identification index A2 is less than the threshold, the identification unit 152 identifies the type of paper as colored paper. Therefore, the identification unit 152 identifies the type of paper to be identified as colored paper.

[0160] On the other hand, the type entered by the user is coated paper. The type identified and the type entered are different. Referring to Figure 10, if the identified type is colored paper and the type entered is coated paper, the modification unit 153 identifies colored paper identification index A1, colored paper identification index A2, coated paper identification index, and recycled pulp identification index as candidates for the identification index of the target.

[0161] First, the modification unit 153 determines whether or not the threshold needs to be adjusted for the colored paper discrimination index A1 among the candidate discrimination indexes for the target. Referring to Figure 17, the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated for colored paper discrimination index A1 is +0.386. For the discrimination unit 152 to discriminate the paper to be discriminated for as coated paper, the measured value for the paper to be discriminated for colored paper discrimination index A1 must be greater than or equal to the threshold (see Figure 9).

[0162] In other words, for the discrimination unit 152 to determine that the paper to be discriminated is coated paper, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 18) in the graph of the colored paper discrimination index A1 shown in Figure 18 must be located on or above the reference lines LA11, LA12. Currently, in the graph of the colored paper discrimination index A1 shown in Figure 18, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 18) is located above the reference lines LA11, LA12. Therefore, the modification unit 153 determines that no threshold adjustment is necessary for the colored paper discrimination index A1 among the candidate discrimination indexes for the target.

[0163] Next, the modification unit 153 determines whether or not the threshold needs to be adjusted for the colored paper discrimination index A2 among the candidate discrimination indexes for the target. Referring to Figure 17, the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated for colored paper discrimination index A2 is -0.024. For the discrimination unit 152 to discriminate the paper to be discriminated for as coated paper, the measured value for the paper to be discriminated for colored paper discrimination index A2 must be greater than or equal to the threshold (see Figure 9).

[0164] In other words, for the discrimination unit 152 to determine that the paper to be discriminated is coated paper, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 19) in the graph of the colored paper discrimination index A2 shown in Figure 19 must be located on or above the reference line LA2. However, currently, in the graph of the colored paper discrimination index A2 shown in Figure 19, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 19) is located below the reference line LA2. Therefore, the modification unit 153 determines that the threshold of the colored paper discrimination index A2 among the candidate discrimination indexes for the target needs to be adjusted, and identifies the colored paper discrimination index A2 as the discrimination index for the target.

[0165] Referring to Figure 23, the step unit of the colored paper discrimination index A2 is 0.03. The modification unit 153 converts the difference between the measured value for the paper to be discriminated in the colored paper discrimination index A2 and the threshold corresponding to the IR transmittance of the paper to be discriminated (in Example 3, -0.024) to the smallest step number that is greater than or equal to the difference (i.e., -1 step) (see Figure 24). The modification unit 153 lowers the threshold for each IR transmittance of the colored paper discrimination index A2 by 1 step all at once.

[0166] As a result, the reference line LA2 in the graph of the colored paper discrimination index A2 shown in Figure 19 moves downward by one step. Figure 28 shows the position of the reference line LA2 in the graph of the colored paper discrimination index A2 before and after the adjustment process for Example 3. The solid line in Figure 28 shows the position of the reference line LA2 in the graph of the colored paper discrimination index A2 before the adjustment process. The dotted line in Figure 28 shows the position of the reference line LA2 in the graph of the colored paper discrimination index A2 after the adjustment process. As shown in Figure 28, the threshold adjustment by the modification unit 153 moves the reference line LA2 from the position shown by the solid line to the position shown by the dotted line. As a result, after the adjustment, in the graph of the colored paper discrimination index A2, the point indicating the measured value for the paper to be discriminated (the point indicated by the triangular mark in Figure 28) is located above the reference line LA2. That is, after the adjustment process, the measured value for the paper to be discriminated in the colored paper discrimination index A2 is greater than or equal to the threshold.

[0167] Next, the modification unit 153 determines whether or not the threshold needs to be adjusted for the coated paper discrimination index among the candidate discrimination indexes for the target. Referring to Figure 17, in the coated paper discrimination index, the difference between the measured value for the paper to be discriminated against and the first threshold corresponding to the IR transmittance of the paper to be discriminated against is -0.026. For the discrimination unit 152 to discriminate that the paper to be discriminated against is coated paper, the measured value for the paper to be discriminated against in the coated paper discrimination index must be equal to or greater than the first threshold (see Figure 9).

[0168] In other words, for the discrimination unit 152 to determine that the paper to be discriminated is coated paper, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 20) must be located above the reference line LB1 in the graph of the coated paper discrimination index shown in Figure 20. However, currently, in the graph of the coated paper discrimination index shown in Figure 20, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 20) is located below the reference line LB1. Therefore, the modification unit 153 determines that the threshold for the coated paper discrimination index among the candidate discrimination indexes for the target needs to be adjusted, and identifies the coated paper discrimination index as the discrimination index for the target.

[0169] Referring to Figure 23, the step unit of the coated paper discrimination index is 0.01. The modification unit 153 converts the difference between the measured value for the paper to be discriminated in the coated paper discrimination index and the first threshold corresponding to the IR transmittance of the paper to be discriminated (in Example 3, -0.026) to the smallest number of steps greater than or equal to the difference (i.e., -3 steps) (see Figure 24). The modification unit 153 lowers the threshold for each IR transmittance of the coated paper discrimination index by 3 steps at once. Since multiple thresholds (a first threshold indicated by the reference line LB1 and a second threshold indicated by the reference line LB2) are set for the coated paper discrimination index, the modification unit 153 lowers these multiple thresholds by 3 steps at once.

[0170] As a result, in the coated paper discrimination index graph shown in Figure 20, the reference lines LB1 and LB2 move downward by 3 steps. Figure 29 shows the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph before and after the adjustment process for Example 3. The solid lines in Figure 29 show the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph before the adjustment process. The dotted lines in Figure 29 show the positions of the reference lines LB1 and LB2 in the coated paper discrimination index graph after the adjustment process. As shown in Figure 29, the threshold adjustment by the modification unit 153 moves the reference lines LB1 and LB2 from the positions shown by the solid lines to the positions shown by the dotted lines. As a result, after the adjustment, in the coated paper discrimination index graph, the point indicating the measured value for the paper to be discriminated (the point indicated by the triangular mark in Figure 29) is located above the reference line LB1. That is, after the adjustment process, in the coated paper discrimination index, the measured value for the paper to be discriminated is greater than or equal to the first threshold.

[0171] Next, the modification unit 153 determines whether or not the threshold of the recycled pulp discrimination index among the candidate discrimination indexes for the target needs to be adjusted. Referring to Figure 17, in the recycled pulp discrimination index, the difference between the measured value for the paper to be discriminated against and the threshold corresponding to the IR transmittance of the paper to be discriminated against is +0.067. For the discrimination unit 152 to discriminate that the paper to be discriminated against is coated paper, the measured value for the paper to be discriminated against in the recycled pulp discrimination index must be greater than or equal to the threshold (see Figure 9).

[0172] In other words, for the discrimination unit 152 to determine that the paper to be discriminated is coated paper, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 21) must be located on or above the reference line LC in the recycled pulp discrimination index graph shown in Figure 21. Currently, in the recycled pulp discrimination index graph shown in Figure 21, the point indicating the measured value for the paper to be discriminated (indicated by the triangular mark in Figure 21) is located above the reference line LC. Therefore, the modification unit 153 determines that no threshold adjustment is necessary for the recycled pulp discrimination index among the candidate discrimination indexes for the target.

[0173] As shown in Figure 24, in Example 3, the threshold for the colored paper discrimination index A2 is lowered by one step collectively, and the threshold for the coated paper discrimination index is lowered by three steps collectively. Therefore, if the discrimination unit 152 performs type discrimination on the paper to be discriminated against again after the adjustment process, the paper to be discriminated against will be identified as coated paper, which is the type entered by the user.

[0174] Furthermore, since each of the multiple thresholds in the coated paper discrimination index (the first threshold indicated by the reference line LB1, and the second threshold indicated by the reference line LB2) is changed by the same amount all at once, the relationship between the multiple thresholds (the first threshold indicated by the reference line LB1 < the second threshold indicated by the reference line LB2) is maintained.

[0175] (E5: Example 4) The adjustment process for Example 4 will now be described. In Example 4, the type of paper to be identified is recycled paper, and the type entered is colored paper.

[0176] Referring to Figures 17 to 21, in Example 4, the measured values ​​for the paper to be identified in the colored paper identification index A1, colored paper identification index A2, and coated paper identification index are equal to or greater than the threshold corresponding to the IR transmittance of the paper to be identified (in the case of the coated paper identification index, the first threshold corresponding to the IR transmittance of the paper to be identified). On the other hand, in Example 4, the measured value for the paper to be identified in the recycled pulp identification index is less than the threshold corresponding to the IR transmittance of the paper to be identified. As shown in Figure 9, the paper type in which the measured values ​​for the colored paper identification index A1, colored paper identification index A2, and coated paper identification index are equal to or greater than the threshold (in the case of the coated paper identification index, the first threshold), and the measured value for the recycled pulp identification index is less than the threshold, is recycled paper. Therefore, the identification unit 152 identifies the type of paper to be identified as recycled paper.

[0177] On the other hand, the type entered by the user is colored paper. The type identified and the type entered are different. Referring to Figure 10, if the identified type is recycled paper and the type entered is colored paper, the modification unit 153 identifies colored paper identification index A1 and colored paper identification index A2 as the identification index for the target.

[0178] Referring to Figure 17, in colored paper discrimination index A1, the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated is +0.072. Referring to Figure 17, in colored paper discrimination index A2, the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated is +0.049.

[0179] As explained with reference to Figure 9, if the measured value in at least one of the colored paper discrimination index A1 and colored paper discrimination index A2 is below the threshold, the discrimination unit 152 determines that the type of paper is colored paper. That is, in order for the discrimination unit 152 to determine that the paper to be discriminated is colored paper, at least one of the following must be true: in the graph of colored paper discrimination index A1 shown in Figure 18, the point indicating the measured value for the paper to be discriminated (the point indicated by the cross mark in Figure 18) is located below the reference lines LA11 and LA12; and in the graph of colored paper discrimination index A2 shown in Figure 19, the point indicating the measured value for the paper to be discriminated (the point indicated by the cross mark in Figure 19) is located below the reference line LA2. However, currently, in the graph of the colored paper discrimination index A1 shown in Figure 18, the point indicating the measured value for the paper being discriminated (the point indicated by the cross mark in Figure 18) is located above the reference lines LA11 and LA12, and in the graph of the colored paper discrimination index A2 shown in Figure 19, the point indicating the measured value for the paper being discriminated (the point indicated by the cross mark in Figure 19) is located above the reference line LA2. Therefore, the modification unit 153 adjusts the thresholds for colored paper discrimination index A1 and colored paper discrimination index A2.

[0180] The modification unit 153 calculates the amount to change the threshold based on the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated, which is the smallest difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated among multiple color paper discriminant indicators. The modification unit 153 changes the threshold for each of the multiple color paper discriminant indicators by the calculated amount at once. This prevents the threshold for each of the multiple color paper discriminant indicators from being changed more than necessary.

[0181] In Example 4, the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated in colored paper discrimination index A2 (+0.049) is smaller than the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated in colored paper discrimination index A1 (+0.072). The modification unit 153 determines the amount of change to the thresholds of colored paper discrimination index A1 and colored paper discrimination index A2 based on the difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated in colored paper discrimination index A2, which has a smaller difference between the measured value for the paper to be discriminated and the threshold corresponding to the IR transmittance of the paper to be discriminated. Referring to Figure 23, the step unit for both colored paper discrimination index A1 and colored paper discrimination index A2 is 0.03. The modification unit 153 converts the difference between the measured value for the paper to be discriminated in the colored paper discrimination index A2 and the threshold corresponding to the IR transmittance of the paper to be discriminated (in Example 4, +0.049) into the smallest number of steps greater than or equal to that difference (i.e., +2 steps) (see Figure 24). The modification unit 153 raises the threshold for each IR transmittance for both the colored paper discrimination index A1 and the colored paper discrimination index A2 by 2 steps collectively.

[0182] As a result, in the graph of the colored paper discrimination index A1 shown in Figure 18, the reference lines LA11 and LA12 move upward by two steps. Also, in the graph of the colored paper discrimination index A2 shown in Figure 19, the reference line LA2 moves upward by two steps.

[0183] Figure 30 shows the positions of the reference lines LA11 and LA12 on the graph of the colored paper discrimination index A1 before and after the adjustment process for Example 4. In Figure 30, the solid lines indicate the positions of the reference lines LA11 and LA12 on the graph of the colored paper discrimination index A1 before the adjustment process. In Figure 30, the dotted lines indicate the positions of the reference lines LA11 and LA12 on the graph of the colored paper discrimination index A1 after the adjustment process.

[0184] FIG. 31 is a diagram showing the position of the reference line LA2 of the graph of the colored paper discrimination index A2 before and after the adjustment process for Example 4. The solid line in FIG. 31 indicates the position of the reference line LA2 of the graph of the colored paper discrimination index A2 before the adjustment process. The dotted line in FIG. 31 indicates the position of the reference line LA2 of the graph of the colored paper discrimination index A2 after the adjustment process.

[0185] As shown in FIG. 30, due to the adjustment of the threshold value by the change part 153, the reference lines LA11 and LA12 move from the position indicated by the solid line to the position indicated by the dotted line. As a result, even after the adjustment, in the graph of the colored paper discrimination index A1, the point indicating the measured value of the paper to be discriminated (the point indicated by the cross mark in FIG. 30) is located above the reference lines LA11 and LA12, similar to before the adjustment.

[0186] On the other hand, as shown in FIG. 31, due to the adjustment of the threshold value by the change part 153, the reference line LA2 moves from the position indicated by the solid line to the position indicated by the dotted line. As a result, after the adjustment, in the graph of the colored paper discrimination index A2, the point indicating the measured value of the paper to be discriminated (the point indicated by the cross mark in FIG. 31) is located below the reference line LA2. That is, after the adjustment process, for the colored paper discrimination index A2, the measured value of the paper to be discriminated is less than the threshold value. <B

[0187] As shown in FIG. 24, in Example 4, for each of the colored paper discrimination index A1 and the colored paper discrimination index A2, the threshold value is uniformly increased by 2 steps. Therefore, when the discrimination unit 152 discriminates the type of the paper to be discriminated again after the adjustment process, the paper to be discriminated is discriminated as the colored paper of the type input by the user.

[0188] <F. Effect> Thus, in this embodiment, the image forming apparatus 1 identifies a discrimination index whose threshold should be changed from among multiple discrimination indices, and changes the threshold of the target discrimination index, so that when the type of recording medium determined differs from the input type, the type of recording medium is determined to be the input type. By repeatedly changing the threshold in this way, the type of recording medium is correctly determined. Therefore, the image forming apparatus 1 in this embodiment can suppress the incorrect determination of the type of recording medium over a wider range.

[0189] Furthermore, compared to a case where the user manually adjusts the threshold of the discrimination index, the image forming apparatus 1 in this embodiment can reduce the effort required from the user.

[0190] [Example 1] In the above embodiment, as an example of distinguishing the type of recording medium from among multiple recording medium types using multiple discrimination indicators, an example was described in which the type of recording medium is distinguished from plain paper, recycled paper, coated paper, and colored paper using colored paper discrimination indicator A1, colored paper discrimination indicator A2, coated paper discrimination indicator, and recycled paper pulp discrimination indicator. However, the multiple discrimination indicators and multiple recording medium types are not limited to these.

[0191] The type of recording medium may be determined from plain paper, recycled paper, coated paper, and colored paper using one colored paper identification index, a coated paper identification index, and a recycled paper pulp identification index.

[0192] Multiple recording media types may include at least two of the following: plain paper, recycled paper, coated paper, and colored paper. For example, a coated paper identification index and a recycled pulp identification index may be used to determine whether the recording media is coated paper, plain paper, or recycled paper.

[0193] Multiple colored paper discrimination indicators may be used to determine whether the recording medium is colored paper or another type of paper.

[0194] Multiple discrimination indicators may include discrimination indicators different from colored paper discrimination indicator A1, colored paper discrimination indicator A2, coated paper discrimination indicator, and recycled paper pulp discrimination indicator, and multiple recording media types may include paper types different from plain paper, recycled paper, coated paper, and colored paper.

[0195] The technology described herein can be applied when determining the type of recording medium from among several types of recording media using multiple discrimination indicators.

[0196] Furthermore, the wavelengths of light emitted by each light source in the light source unit 21 described in the above embodiment are merely examples. The light emitted by each light source should have a wavelength that allows for the identification of the type of recording medium from among multiple types of recording media, and should be determined according to the multiple discrimination indicators used.

[0197] The wavelengths of light used to distinguish between colored paper are not limited to those shown in Figures 5 and 6. The wavelengths of light used to distinguish between colored paper are determined according to the color of the paper to be distinguished.

[0198] [Differentiation 2] In the above embodiment, the modification unit 153 determined the amount of change to the threshold of the discrimination index for a single sheet of paper to be discriminated based on the measured value of the discrimination index for that sheet. In the modified example 2, the modification unit 153 may determine the amount of change to the threshold of the discrimination index for a multiple sheet of paper to be discriminated based on the measured value of the discrimination index for that sheet. For example, the modification unit 153 may determine the amount of change to the threshold of the discrimination index for a multiple sheet of paper to be discriminated based on the average value of the measured values ​​of the discrimination index for that sheet.

[0199] As a result, the amount of change in the threshold of the discrimination index is determined based on measurements from multiple sheets of paper, thus ensuring reliability of the change amount. Consequently, the image forming apparatus 1 in modified example 2 can suppress the misidentification of the type of recording medium over a wider range.

[0200] Furthermore, the number of recording media used to determine the threshold change amount may be predetermined or specified by the user. If the user specifies the number of recording media used to determine the threshold change amount, the input unit 51 may accept an operation to input the number of recording media used to determine the threshold change amount. More specifically, as shown in Figure 32, a field for inputting the number of recording media used to determine the threshold change amount is provided on the screen that accepts an operation to input the type of recording media.

[0201] Figure 32 shows an example of a screen that accepts input for the type of recording medium in Modification 2. Screen G5 is a screen for selecting the type of recording medium from among several types of recording media, similar to screen G2 shown in Figure 14. Screen G5 is displayed on the display unit 52. The difference between screen G5 and screen G2 shown in Figure 14 is that screen G5 includes an input field m6 for inputting the number of recording media to be used to determine the threshold change amount. When the user presses button B3 corresponding to the type of recording medium, enters a number in input field m6, and presses button B4, the processor 11 accepts the type corresponding to button B3 pressed by the user as the type of recording medium, and accepts the number entered in input field m6 as the number of recording media to be used to determine the threshold change amount.

[0202] [Note] The embodiments and variations described above include the following technical concepts.

[0203] [Configuration 1] Regarding the recording medium, the acquisition unit acquires the measured values ​​of each of the multiple discrimination indicators used to determine the type of recording medium, A discrimination unit that determines the type of recording medium from among multiple types of recording media based on the comparison result between the measured value and the threshold for each of the multiple discrimination indicators, An input unit that accepts an operation to input the type of recording medium, A discrimination device comprising: a determination device that, when the determined type and the input type are different, identifies a determination indicator from among a plurality of determination indicators to change the threshold of so that the type of the recording medium is determined to be the input type, and a modification unit that changes the threshold of the determination indicator to be changed.

[0204] [Configuration 2] The discrimination device according to configuration 1, wherein the plurality of recording media types include at least two of plain paper, recycled paper, coated paper, and colored paper.

[0205] [Configuration 3] Each of the aforementioned multiple discrimination indicators is the relative value of the transmittance of two types of light with different wavelengths, or the relative value of the reflectance of the two types of light. The discrimination device according to configuration 1 or 2, wherein the threshold value of each of the plurality of discrimination indicators is set according to the IR transmittance, which is the infrared transmittance of the recording medium.

[0206] [Structure 4] The modification unit changes the threshold values ​​for each IR transmittance of the target discrimination index by the same amount all at once, as described in configuration 3 of the discrimination device.

[0207] [Composition 5] The modification unit determines the amount of change to the threshold based on the difference between the measured value and the threshold corresponding to the IR transmittance of the recording medium, as described in configuration 4.

[0208] [Composition 6] The modification unit determines the amount of change to the threshold based on the measured values ​​of the target discrimination index for multiple recording media, as described in configuration 1 or 2.

[0209] [Composition 7] The determination device according to configuration 6, wherein the input unit accepts an operation to input the number of recording media used to determine the amount of change.

[0210] [Structure 8] If the aforementioned multiple recording media types include colored paper, the aforementioned multiple discrimination indicators include multiple colored paper discrimination indicators. The aforementioned discrimination unit is If the measured value of at least one of the multiple colored paper discrimination indicators indicates a colored paper, the recording medium is identified as a colored paper. If none of the above-mentioned colored paper discrimination indicators have measured values ​​indicating colored paper, the recording medium is determined to be something other than colored paper. The determination device according to configuration 1 or 2, wherein the modification unit, when the recording medium is determined to be something other than colored paper and the input type is colored paper, identifies the plurality of colored paper determination indicators as the determination indicator for the target, calculates the amount of change to the threshold based on the difference between the measured value and the threshold of the colored paper determination indicator with the smallest difference among the plurality of colored paper determination indicators, and changes the threshold for each of the plurality of colored paper determination indicators by the amount of change.

[0211] [Composition 9] The modification unit modifies, if multiple thresholds are set for the discrimination index of the target, all of the multiple thresholds are changed by the same amount at once, as described in any one of configurations 1 to 8, the discrimination device.

[0212] [Configuration 10] The discrimination device according to configuration 3, wherein the relationship between the threshold and the IR transmittance is expressed by a linear function.

[0213] [Composition 11] The determination device according to configuration 5, wherein the modification unit converts the difference into a number of steps based on a predetermined step unit, and determines the number of steps as the amount of change.

[0214] [Composition 12] The discrimination device according to configuration 5, further comprising a display unit for displaying the amount of change.

[0215] [Composition 13] The discrimination device further includes a display unit that displays a screen for selecting the type of recording medium from among the plurality of recording medium types, The discrimination device described in any one of configurations 1 to 12 accepts the type of recording medium according to user operations performed on the screen.

[0216] [Composition 14] Regarding recording media, the measurement values ​​of each of the multiple discrimination indicators used to determine the type of recording media are obtained, Based on the comparison result between the measured value and the threshold for each of the aforementioned multiple discrimination indicators, the type of recording medium is determined from among the multiple types of recording media. The system accepts an operation to input the type of recording medium, A discrimination method comprising: identifying a discrimination indicator among a plurality of discrimination indicators whose threshold should be changed, and changing the threshold of the discrimination indicator to be changed, in the event that the type of the recording medium is determined to be the type of the input, when the type that has been determined is different from the type that has been input.

[0217] [Composition 15] A discrimination program that causes a computer to execute the discrimination method described in Configuration 14.

[0218] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0219] 1 Image forming apparatus, 10 Control device, 11 Processor, 12 Memory, 13 Storage, 15 Paper feed unit, 20 Media sensor, 21 Light source unit, 21X, 21Y, 211, 212, 213, 214, 215 Light source, 22 Light receiving sensor, 23X, 23Y Substrate, 24 Reflector, 30 Image forming unit, 31 Intermediate transfer belt, 32 Image forming unit, 33 Transfer roller, 40 Fixing unit, 50 Operation panel, 51 Input unit, 52 Display unit, 60 Communication interface, 83 Tray, 99 Bus, 131 Program, 132 Threshold information, 151 Acquisition unit, 152 Discrimination unit, 153 Change unit, 500 External device, AR Arrow, B1, B2, B3, B4, B5 Button, G1, G2, G3, G4, G5 Screen, LA2, LA11, LA12, LB1, LB2, LC reference line, P paper, m1, m2, m3, m4, m5 information, m6 input field.

Claims

1. Regarding the recording medium, the acquisition unit acquires the measured values ​​of each of the multiple discrimination indicators used to determine the type of recording medium, A discrimination unit that determines the type of recording medium from among multiple types of recording media based on the comparison result between the measured value and the threshold for each of the multiple discrimination indicators, An input unit that accepts an operation to input the type of recording medium, The system includes a modification unit that, when the type identified differs from the type entered, identifies a discrimination index among the plurality of discrimination indexes whose threshold should be changed so that the type of the recording medium is identified as the type entered, and modifies the threshold of the selected discrimination index by an amount based on the difference between the measured value and the threshold, The aforementioned multiple recording media types include colored paper, The aforementioned multiple discrimination indicators include multiple colored paper discrimination indicators, The aforementioned discrimination unit is If the measured value of at least one of the multiple colored paper discrimination indicators indicates a colored paper, the recording medium is identified as a colored paper. If none of the above-mentioned colored paper discrimination indicators have measured values ​​indicating colored paper, the recording medium is determined to be something other than colored paper. The modification unit, when the recording medium is determined to be something other than colored paper and the input type is colored paper, identifies the plurality of colored paper discrimination indicators as the discrimination indicator for the target, calculates the amount of change to the threshold for the plurality of colored paper discrimination indicators based on the difference between the measured value and the threshold of the colored paper discrimination indicator with the smallest difference among the plurality of colored paper discrimination indicators, and changes the threshold for each of the plurality of colored paper discrimination indicators by the amount of change.

2. The discrimination device according to claim 1, wherein the plurality of recording media types further include at least one of plain paper, recycled paper, and coated paper.

3. Each of the aforementioned multiple discrimination indicators is the relative value of the transmittance of two types of light with different wavelengths, or the relative value of the reflectance of the two types of light. The discrimination device according to claim 1 or 2, wherein each of the threshold values ​​of the plurality of discrimination indicators is set according to the IR transmittance, which is the infrared transmittance of the recording medium.

4. The discriminant device according to claim 3, wherein the modification unit changes the threshold values ​​for each IR transmittance of the target discriminant index by the same amount all at once.

5. The discriminant device according to claim 4, wherein the modifying unit determines the amount of change to the threshold based on the difference between the measured value and the threshold corresponding to the IR transmittance of the recording medium.

6. The discriminant device according to claim 1 or 2, wherein the modification unit determines the amount of change to the threshold based on the measured value of the target discriminant index for a plurality of recording media.

7. The determination device according to claim 6, wherein the input unit accepts an operation to input the number of recording media used to determine the amount of change.

8. The discrimination device according to claim 1 or 2, wherein the modification unit modifies the multiple thresholds by the same amount at once when multiple thresholds are set for the discrimination index of the target.

9. The discrimination device according to claim 3, wherein the relationship between the threshold and the IR transmittance is expressed by a linear function.

10. The determination device according to claim 5, wherein the modification unit converts the difference into a number of steps based on a predetermined step unit, and determines the number of steps as the amount of change.

11. The discrimination device according to claim 5, further comprising a display unit for displaying the amount of change.

12. The discrimination device further includes a display unit that displays a screen for selecting the type of recording medium from among the plurality of recording medium types, The discrimination device according to claim 1 or 2, wherein the discrimination device accepts the type of recording medium in accordance with the user's operation performed on the screen.

13. Regarding recording media, the measurement values ​​of each of the multiple discrimination indicators used to determine the type of recording media are obtained, Based on the comparison result between the measured value and the threshold for each of the aforementioned multiple discrimination indicators, the type of recording medium is determined from among the multiple types of recording media. The system accepts an operation to input the type of recording medium, If the type identified differs from the type entered, the system includes identifying a discrimination index among the plurality of discrimination indexes whose threshold should be changed so that the type of recording medium is identified as the type entered, and changing the threshold of the discrimination index to be changed by an amount based on the difference between the measured value and the threshold, The aforementioned multiple recording media types include colored paper, The aforementioned multiple discrimination indicators include multiple colored paper discrimination indicators, The above determination is, If the measured value of at least one of the aforementioned multiple colored paper discrimination indicators indicates a colored paper, the recording medium is to be identified as a colored paper. If the measured value of any of the aforementioned colored paper discrimination indicators does not indicate a colored paper, the recording medium is determined to be something other than a colored paper. The method for making the change includes, if the recording medium is determined to be something other than colored paper and the input type is colored paper, identifying the plurality of colored paper discrimination indicators as the discrimination indicators for the target, calculating the amount of change to the threshold for the plurality of colored paper discrimination indicators based on the difference between the measured value and the threshold of the colored paper discrimination indicator with the smallest difference among the plurality of colored paper discrimination indicators, and changing the threshold for each of the plurality of colored paper discrimination indicators by the amount of change.

14. A discrimination program that causes a computer to execute the discrimination method described in claim 13.

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